This is normal - when you are inside MEASURE command with Distance option the question mark appears at crosshairs. When you use menu Tools -> Inquiry -> Distance menu you actually call MEASUREMENT command with Distance option. After you pick two points you can see the results of the measurement at the command window, than AutoCAD asks you to measure another distance.
In order to quit command and "clear" the question mark you need to hit Esc key on the keyboard.

Maxim